The process of sexual differentiation of the brain into a male or female type occurs during the early postnatal period in rodents. This process is critically dependent upon the steroid hormones testosterone and estrogen. Despite knowledge of the major factors involved in brain sexual differentiation, little is known about the molecular mechanisms involved. To address this question, we plan to use the technique of differential display to identify cDNAs synthesized during brain sexual differentiation, in particular, cDNAs which are different in the male vs. female brain, and cDNAs that are stimulated by androgen treatment of female animals. The differential display technique involves amplification of cDNAs corresponding to mRNAs from two different samples. The amplified cDNAs are run on a gel, and bands that differ between the two samples are then identified. Differentially expressed cDNAs will be sequenced and patterns of expression determined by in situ hybridization. Antisense techniques will then be used to block the translation of differentially expressed mRNAs, followed by morphological and functional assessment of sexual differentiation. This project is being terminated here since Dr. McCarthy is doing the bulk of the work at the University of Maryland. We will continue to collaborate with her as needed.